X-ray investigations and magnetic field effect on a nematic phase of disc-like molecules

Abstract

The X-ray diffraction patterns of powder samples of the fluid mesophase of the hexaalkoxybenzoates of triphenylene which is a disc-like molecule are similar to the diffraction patterns of non orientated nematic phase of rod-like molecules. Furthermore, we give evidence for a uniaxial character of this anisotropic medium with a negative diamagnetic anisotropy, the flat molecules are orientated parallel each other by a rotating magnetic field. In addition, the X-ray patterns of orientated samples of the hexyloxy compound revealed pretransitional effects in this nematic phase of disc-like molecules (ND). This short-range translational order, sort of skewed cybotactic groups originates from the existence of a low temperature columnar phase with an original tilted packing here described.